Seat base



FIG. 1 is a perspective view of a seat base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a side view thereof; and,

FIG. 6 is another perspective view shown with environmental structure.

The broken lines showing of a seat and wheels in FIG. 6 are for illustrative purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a seat base, as shown and described. 